If you or your child have been prescribed thiamine, follow the doctor's instructions when taking it.
If you have bought thiamine from a pharmacy or a shop, follow the instructions that come with the packet.
Dosage and strength
Thiamine comes as tablets containing 50mg or 100mg of thiamine. It also comes as slow-release tablets containing 100mg of thiamine and as a liquid containing 100mg in 5ml.
Your dose depends on why you need thiamine and whether it's been prescribed by a doctor.
Mild thiamine deficiency
The usual dose for adults is between 25mg and 100mg, taken once a day.
Severe thiamine deficiency
The usual dose for adults is 100mg, taken 2 or 3 times a day.
Dose for children
If your child is prescribed thiamine, the doctor will use your child's weight to work out the right dose.
Changes to your dose
For treating a vitamin B1 deficiency, your dose will usually stay the same until your levels are back to normal and your symptoms improve.
Once your levels are OK, your doctor will probably put you on a lower dose to make sure you do not become deficient again.
How to take it
You can take thiamine with or without food.
Swallow the tablet whole with a drink of water. If you find tablets difficult to take, break the tablet in half using the line down the middle. Take both halves separately.
How long to take it for
If a doctor has prescribed thiamine to treat a vitamin B1 deficiency, you need to keep taking it until your levels have increased to normal again and your symptoms are better.
Many people who become deficient in vitamin B1 cannot absorb enough of the vitamin from their normal diet. They may need to continue taking a low dose of thiamine for a long time to prevent them from becoming deficient again.
The doctor will advise you on how much to take and how long for.
Speak to your doctor if you've been prescribed thiamine and you want to stop taking it for any reason.
If you forget to take it
Missing 1 or 2 doses will probably not matter too much. But if you have a vitamin deficiency and you keep forgetting to take your thiamine, ask a doctor for advice.
If you forget to take your thiamine, take the missed dose as soon as you remember, unless it's nearly time for your next dose. In this case skip the missed dose and just take the next one at the usual time.
Do not take 2 doses to make up for a forgotten one.
If you forget doses often, it may help to set an alarm to remind you. You could also ask a pharmacist for advice on other ways to help you remember to take your medicine.
If you take too much
Thiamine is generally a very safe medicine. Taking too much is unlikely to harm you or your child.
If you're worried, speak to a pharmacist or doctor.